JS Async Callback

asyncFindUser.js

function findUser(id) {
    let user;
    setTimeout(function() {
        console.log("waited 0.1 sec.");
        user = {
            id: id,
            name: "User" + id,
            email: id + "@test.com"
        };
    }, 100);
    return user;
}

const user = findUser(1);
console.log("user:", user);

asyncFindUserAndCallBack.js

function findUserAndCallBack(id, cb) {
    setTimeout(function() {
        console.log("waited 0.1 sec.");
        const user = {
            id: id,
            name: "User" + id,
            email: id + "@test.com"
        };
        cb(user);
    }, 100);
}

findUserAndCallBack(1, function(user) {
    console.log("user:", user);
});

syncFindUser.js

function findUser(id) {
    const user = {
        id: id,
        name: "User" + id,
        email: id + "@test.com"
    };
    return user;
}

const user = findUser(1);
console.log("user:", user);

syncFindUserAndCallBack.js

function findUserAndCallBack(id, cb) {
    const user = {
        id: id,
        name: "User" + id,
        email: id + "@test.com"
    };
    cb(user);
}

findUserAndCallBack(1, function(user) {
    console.log("user:", user);
});